zoom-window

Arguments:
window &optional new-state

Changes the state
of window to new-state,
which must be one of nil (the default),
:maximized, or :normal. nil means toggle between :normal
and :maximized.

This operator is
now a non-generic function. It calls (setf state), which is
a generic function to effect the change in its argument's state. If
you added methods to this operator, you should modify them to be
methods on (setf state). (See expand-window for an example.)